The present invention relates in general to the design of a fluid filter which includes a stamped steel nutplate for threaded attachment to a filter head. More specifically, the present invention relates to a fluid filter design wherein the nutplate has a threaded aperture which is larger, compared to earlier designs, in order to provide a reduced moment arm. Included in the disclosed design of the present invention are novel inner and outer seals which provide improved performance characteristics. The anticipated use for the present invention is in cooperation with a vehicle engine such as a diesel engine.
A related embodiment of the present invention is directed to the spin-on filter and the filter head interface. More specifically, this related embodiment includes a design relationship for the specific sequence of thread and seal (inner and outer) engagements between the fluid filter and the filter head in order to facilitate easier installation.
While the design of fluid filters over the years has involved literally hundreds of different concepts, the basic principles of operation have remained much the same. The fluid substance to be filtered must first be introduced into the filter housing or shell and from there directed to flow into and through the filtering media. As the filtered fluid exits from the filtering media, it needs to be routed to a flow outlet. Throughout this flow loop, it is generally preferred that the unfiltered fluid not by-pass the filtering media and that fluid not leak from the filter shell. While these functions can normally be achieved by the use of properly designed and positioned seals, over time seals deteriorate and leakage can occur. The passage of time and continued use can also cause deterioration of other components and interfaces within the fluid filter. For example, each pulse of fluid pressure creates a variable load on the nutplate causing it to flex. The flexing of the nutplate creates wear in the plate and weakens nutplate interfaces and deterioration begins. In particular, the flexing causes the outer seal to deflect which in turn can create a leakage interface. To some extent the rate of deterioration is affected by the operating environment and the nature of the substance being filtered. If a longer service interval is desired for the filter assembly, it is important to be able to slow the rate of deterioration.
In order to provide a representative sampling of earlier fluid filter assembly designs, the following listed patents should be considered:
______________________________________ U.S. Pat. No. PATENTEE ISSUE DATE ______________________________________ 4,841,628 Nagle Jun. 27, 1989 4,839,037 Bertelsen et al. Jun. 13, 1989 4,855,047 Firth Aug. 8, 1989 5,118,417 Deibel Jun. 2, 1992 5,548,893 Koelfgen Aug. 27, 1996 4,992,166 Lowsky et al. Feb. 12, 1991 5,171,430 Beach et al. Dec. 15, 1992 5,395,518 Gulsvig Mar. 7, 1995 4,052,307 Humbert, Jr. Oct. 4, 1977 1,033,858 Adams Jul. 30, 1912 2,646,886 Le Clair Jul. 28, 1953 2,743,019 Kovacs Apr. 24, 1956 3,859,216 Sisson et al. Jan. 7, 1975 5,300,223 Wright Apr. 5, 1994 5,445,734 Chen Aug. 29, 1995 1,647,799 Hammer Nov. 1, 1927 ______________________________________
In those diesel engine filter designs which employ an internally threaded nutplate, one of the design concerns is the type and level of vibration which the filter assembly sees in its actual use environment. In a typical installation, the fluid filter assembly is threadedly attached to a mounting base or filter head. The filter head typically provides the flow passages for the incoming (unfiltered) fluid as well as a flow passage for the exiting (filtered) fluid. An externally threaded, hollow stem is typically used in order to threadedly mate with an internally threaded aperture in the nutplate. Since the threaded stem is hollow, it is constructed and arranged to function as an exit flow passage or conduit.
Vibrations due to engine operation and those coming from road conditions are transmitted to the fluid filter assembly by means of the filter mounting base and the threaded stem. The distance from the outside diameter of the threaded stem to the filter housing (i.e., shell) defines a moment arm about which the filter assembly is able to move. The greater the length of the moment arm, the greater the amplitude of the transmitted vibrations and the greater the rate of deterioration of the seals of the fluid filter assembly and in turn the greater the rate of deterioration of the filter assembly. Vibrations of the type described also have a deterioration effect on the seals, the nutplate and other structural components of the fluid filter. In order to increase the useful life of the fluid filter assembly, it would be desirable to reduce the length of the moment arm. This is accomplished by the present invention by increasing the size of the internally threaded aperture in the nutplate and in turn by providing an internally-threaded mounting portion with an increased outside diameter.
By employing a nutplate with the same outside diameter, an increase in the inside diameter size reduces the radial thickness or width of the nutplate sidewall and in turn reduces the available area which can be used for drilling, molding, or otherwise incorporating fluid flow holes. The inside and outside diameters of the nutplate define the sidewall which has an annular ring shape. While flow holes could conceivably be provided in this annular ring area, each flow hole would, by necessity, have to be quite small. In order to have enough flow area for adequate and efficient flow through the fluid filter, a relatively large number of these smaller holes is required. As the number of holes increases, the spacing between holes decreases and this would significantly weaken the nutplate. Consequently, a modified design needs to be provided for the nutplate and for the cooperating filter seals in order to provide for the necessary flow of unfiltered fluid into the fluid filter assembly. These modified designs are provided by the present invention in a novel and unobvious manner. As will be described, there are four different inner seals disclosed in order to cooperate with the various nutplate embodiments of the present invention.
The nutplate designs of the present invention are disclosed in various arrangements and for each one there is a specifically styled inner seal. Each inner seal design is positioned over the end of the filtering element and around an exit flow conduit which is part of the engine block mounting base. One style of inner seal cooperates with one style of nutplate of the primary embodiment in order to create flow passageways therebetween through alternating open sections in the seal. In the other style of inner seal, the flow passageways which are defined between the nutplate and the inner seal are created by the use of depending projections from the lower wall of the nutplate. Otherwise, the two inner seals function in a similar fashion. In the related embodiment of the fluid filter, one style of inner seal cooperates with the mounting base and radial flow areas are created between the nutplate and the filter element. The other style of inner seal for this related embodiment includes its own flow passageways as well as cooperating with the nutplate for the creation of radial flow areas.
The outer seal provides a sealed interface between the mounting base and the outer shell which is formed over the upper annular portion of the nutplate, outward of the location of the threaded connection. The outer seal is uniquely styled with a pair of circumferential ribs for sealing redundancy. The outer seal also helps to dampen vibrations which may be transmitted by the mounting base. The cooperation of the inner and outer seals with the nutplate styles of the present invention provides an improved fluid filter assembly.